Recent innovation in the field of genetic engineering has been remarkable. In particular, the development of a polymerase chain reaction (PCR) method has enabled the mass replication of target DNA. The PCR method is based on the principle that DNA polymerase does not function without a primer. The PCR method is used to amplify DNA in large amounts by repeating the following cycle: (1) DNA in a sample is heat denaturated resulting in single stranded DNA, (2) a primer is bonded to the DNA under reduced temperature and (3) the DNA is formed by thermo-stable DNA polymerase under this condition. Consequently, target DNA can be prepared in large amounts by using a specific primer prepared by chemical synthesis or otherwise. In this method, the replication of target DNA is typically monitored by electrophoresis.